Sieve Email Filtering: Sieves and Display Directives in XML
RFC 5784

Internet Engineering Task Force (IETF)                          N. Freed
Request for Comments: 5784                                      S. Vedam
Category: Standards Track                               Sun Microsystems
ISSN: 2070-1721                                               March 2010

      Sieve Email Filtering:  Sieves and Display Directives in XML

Abstract

   This document describes a way to represent Sieve email filtering
   language scripts in XML.  Representing Sieves in XML is intended not
   as an alternate storage format for Sieve but rather as a means to
   facilitate manipulation of scripts using XML tools.

   The XML representation also defines additional elements that have no
   counterparts in the regular Sieve language.  These elements are
   intended for use by graphical user interfaces and provide facilities
   for labeling or grouping sections of a script so they can be
   displayed more conveniently.  These elements are represented as
   specially structured comments in regular Sieve format.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5784.

Freed & Vedam                Standards Track                    [Page 1]
RFC 5784             An XML Representation for Sieve          March 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
   3.  Grammatical Structure of Sieve . . . . . . . . . . . . . . . .  4
   4.  XML Representation of Sieve  . . . . . . . . . . . . . . . . .  6
     4.1.  XML Display Directives . . . . . . . . . . . . . . . . . .  9
     4.2.  Structured Comments  . . . . . . . . . . . . . . . . . . . 10
     4.3.  Validation . . . . . . . . . . . . . . . . . . . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Extended Example  . . . . . . . . . . . . . . . . . . 14
   Appendix B.  XML Schema for Sieves in XML  . . . . . . . . . . . . 21
   Appendix C.  Relax NG Schema for Sieves in XML . . . . . . . . . . 24
   Appendix D.  Stylesheet for Conversion from XML  . . . . . . . . . 26
   Appendix E.  Acknowledgements  . . . . . . . . . . . . . . . . . . 32

Freed & Vedam                Standards Track                    [Page 2]
RFC 5784             An XML Representation for Sieve          March 2010

1.  Introduction

   Sieve [RFC5228] is a language for filtering email messages at or
   around the time of final delivery.  It is designed to be
   implementable on either a mail client or mail server.  It is meant to
   be extensible, simple, and independent of access protocol, mail
   architecture, and operating system, and it is intended to be
   manipulated by a variety of different user interfaces.

   Some user interface environments have extensive existing facilities
   for manipulating material represented in XML [XML].  While adding
   support for alternate data syntaxes may be possible in most if not
   all of these environments, it may not be particularly convenient to
   do so.  The obvious way to deal with this issue is to map Sieves into
   XML, possibly on a separate back-end system, manipulate the XML, and
   convert it back to normal Sieve format.

   The fact that conversion into and out of XML may be done as a